Optical fibre Bragg distributed gratings

An optical fiber amplifier having a signal input port, a signal output port, an optical pump source and a length of optically amplifying waveguide optically pumped by the optical pump source via a wavelength multiplexer, which multiplexer includes a 2.times.2 single mode tapered fused fiber coupler formed from two single mode optical fibers of substantially identical cross-section secured together in side-by-side contact over a length that includes sequentially a first portion where the fibers are drawn down to an extent providing substantially 3 dB mutual coupling between the two fibers at a signal wavelength optically amplified by the optically amplifying wavelength, and a second portion in which there is substantially no mutual coupling between the fibers and in which second portion substantially identical Bragg distributed gratings are formed in both fibers equidistant from said first portion, the periodicity of which gratings renders them spectrally selectively reflecting to light propagating in the two fibers at said signal wavelength.

A method of making an optical fiber element from two single mode optical fibers of substantially identical cross-section, in which method the two fibers are fused together in side-by-side contact over a specific length thereof, wherein mutual coupling between the two fibers over a first portion of said length is created by drawing them down using a set of progressive stretching operations upon the fibers while they are traversed longitudinally through a localized hot zone in which they are locally heat-softened, and wherein, at a second portion of said length beyond said first portion, Bragg distributed gratings are created simultaneously in both fibers equidistant from said first portion.